Doherty Power Amplifier Combiner Using Open Coupled Microstrip Lines
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Solution Overview
Problem
Traditional Doherty power amplifiers suffer from narrow bandwidth performance, fixed impedance characteristics, and lack of harmonic suppression, particularly in broadband applications and for Gallium Nitride (GaN) High Electron Mobility Transistor (HEMT) designs, limiting their efficiency and linearity.
Innovation Solution
A Doherty power amplifier configuration with a combiner that uses open coupled microstrip lines and quarter wavelength transmission lines, allowing for flexible impedance matching and termination, and providing broad bandwidth and harmonic suppression through adjustable electrical lengths and U-shaped folded structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If quarter wavelength transmission lines are used in the combiner, then impedance transformation is achieved at center frequency, but bandwidth is limited
Solution Approach 1:
The combiner is divided into multiple functional sections: input coupling section with open coupled microstrip lines, impedance transformation section with quarter wavelength lines, and output coupling section. Each section performs a specific function, allowing independent optimization of bandwidth and impedance matching precision.
Solution Approach 2:
The patent transitions from traditional single-dimensional quarter wavelength lines to two-dimensional open coupled microstrip line structures. This dimensional change enables broader bandwidth while maintaining impedance transformation capabilities through coupled resonance effects.
2Ease of manufacture
If traditional combiner structures are used, then simple implementation is achieved, but harmonic suppression is insufficient
Solution Approach 1:
The patent converts the potentially harmful harmonic frequencies into beneficial effects by using open coupled microstrip lines that provide harmonic suppression. The coupled resonance structure naturally attenuates even harmonics while maintaining fundamental frequency performance, turning a design challenge into a performance advantage.
3Device complexity
If fixed impedance characteristics are used, then design simplicity is maintained, but flexibility for different applications is reduced
Solution Approach 1:
The combiner design enables dynamic impedance characteristics through the open coupled microstrip lines, which can be tuned to provide different impedance transformations depending on operating conditions. This dynamic behavior allows the same structure to adapt to various application requirements without increasing design complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution achieves a broader balanced amplitude bandwidth, controllable combiner size, and significant 2nd harmonic suppression, enhancing the power amplifier's efficiency and linearity while meeting product spectrum mask requirements.
Implementation Method 1
a first input port and a termination port are open coupled by at least two coupled microstrip lines and/or the second input port and the output port are open coupled by at least two coupled microstrip lines; while the first input port and the second input port are connected by a quarter wavelength transmission line and/or the termination port and the output port are connected by a quarter wavelength transmission line
Data Source
AI summary
A Doherty power amplifier and a device are disclosed. In a combiner of the Doherty power amplifier, a first input port and a termination port are open coupled by at least two coupled microstrip lines and/or a second input port and an output port are open coupled by at least two coupled microstrip lines. Therefore, a balanced amplitude bandwidth may be obtained and may be much broader than that of the existing solutions, in addition, a controllable size or a potentially small size may be realized. Furthermore, the Doherty power amplifier in this disclosure may provide large 2nd harmonic suppression to meet product spectrum mask requirements.